The method used in predicate systems for detecting faults in the shields of electrosurgical instruments is sensitive only to the current in the shield. Furthermore, existing systems rely heavily on analog circuits and associated monitoring techniques that result in limitations in how the existence of a shield fault is detected, communicated to a user, and delivered to the ESU for deactivation. Examples include devices and methods such as those disclosed in U.S. Pat. Nos. 5,312,401 and 5,688,269, commonly assigned with the present application to Encision, Inc. of Boulder, Colo.
Illustrated in FIG. 1 is an example of a laparoscopic electrosurgical apparatus as is known in the prior art. A tubular safety shield assembly 25 includes a tubular shield 20 having a layer of insulation 22 provided on the outer surface thereof and an optional layer of insulation 24 provided on the inner surface thereof. The tubular shield assembly is inserted through trocar sheath 10 to thereby provide a passageway through which the active electrode probe 12 may be inserted. An elongated port 31 may extend through the active electrode through which irrigation fluids, suction, a pressurized gas stream, etc. may pass. When active probe 12 and tubular shield assembly 25 are in their respective inserted positions as shown in FIG. 1, the shield 20 surrounds the active probe from at least (a) a proximal point 26 prior to the entry point 28 of the active probe into the trocar sheath 10 to (b) a distal point 30 in proximity to the tip 18 of the active probe.
Shield monitor circuitry 32 is connected to shield 20 via a dual conductor lead 34 whereby the integrity of the connection of the shield to the monitor circuitry can be monitored.
The active electrode probe 12 is connected to an electrosurgical generator 36 via an active lead 38. The electrosurgical generator is connected to a patient return electrode 40, via the shield monitor circuitry 32 and, in particular, the return terminal of the generator is connected to circuitry 32 via lead 35 while the circuitry 32 is connected to the return electrode via lead 37. Upon detection of a fault condition by the shield monitor circuitry, the electrosurgical generator 36 may be deactivated by opening a relay in the connection between the generator and patient return electrode 40 although other means may also be employed to deactivate the generator.
As can be appreciated by those of skill in the art, the prior art as described herein only provides the ability to detect a fault condition based on sensing the current in the shield and thus does not provide a great deal of flexibility to the surgeon to account for the use of modern electrosurgical instruments and varying surgical procedures that might benefit from a monitoring device that is capable of detecting faults based on other radio frequency parameters. Such benefits may include earlier fault detection of or detection of a fault at lower ESU power settings. In addition, the limitations imposed by the use of analog sensing electronics and associated processing schemes make more sophisticated monitoring techniques difficult and make it more difficult to customize the fault detection process for varying situations where one fault threshold may not be adequate or appropriate.